1. Field of the Invention
The present invention is generally related to a fuel supply system for an internal combustion engine and, more particularly, to a fuel supply system that reduces the temperature of the fuel as the fuel is recirculated prior to flowing to a fuel injection system for an internal combustion engine.
2. Description of the Prior Art
Many different types of fuel supply systems are well known to those skilled in the art. In certain types of fuel supply systems which are used in conjunction with marine vessels, the fuel system supplies fuel from a boat fuel tank to an electronic fuel injection system for an internal combustion engine used to propel the boat. Fuel is provided to the fuel injectors which inject fuel into cylinder air intake runners at a relatively constant pressure above the air intake manifold pressure. In engines which use continuous-duty fuel pumps, excess fuel which is not immediately needed by the fuel injectors is typically returned to a main fuel tank or recirculated for subsequent injection by the fuel injectors.
In systems that use vapor separators, the vapor separator is typically located in the fuel line between the fuel tank and the engine and usually comprises a container into which the fuel is pumped. The purpose of vapor separators is to remove vapor or air from the fuel stream so that liquid fuel is present on the upstream, or low pressure, side of the fuel pump. The purpose of a fuel vapor separator is to prevent vapor lock from occurring. If a vapor separator is not used, pump vapor lock can occur, particularly when the engine is idling, due to heat generated in the fuel stream by the electric fuel pump or because of engine heat soak after the engine has been shut down and restarted after a relatively short period of time. Since gasoline boils or vaporizes easily at atmospheric pressures, a fuel supply system that does not include a vapor separator, must efficiently cool the fuel to avoid vapor lock.
U.S. Pat. No. 3,835,822, which issued to Mickle et al on Sep. 17, 1974, discloses a cooled fuel pump for an internal combustion engine. The fuel pump is intended for use with water-cooled marine engines and includes a cast aluminum housing. A water cooling tube is imbedded in the housing connected directly to the inlet of the main cooling system for the engine such that upon initial starting of the engine, cooling water is immediately supplied to the fuel pump to reduce its temperature, and thereby eliminate vapor lock conditions. The tube may be formed of suitable material to minimize electrolytic conditions with respect to the cast housing and prevent possible leakage of water into the fuel system.
U.S. Pat. No. 4,768,492, which issued to Widmer et al on Sep. 6, 1988, describes a marine propulsion system with a fuel line cooler. The cooler is provided for a marine propulsion system having a water cooled internal combustion engine in a heat retentive compartment. The fuel line cooler has an inlet in communication with the source of cooling water for the engine, and has an outlet for discharging water. The fuel line cooler is cooled by sea water during running of the engine. Upon turning off the engine, the cooled water in the fuel line cooler is in heat transfer relation with the fuel and prevents vaporization and/or spewing of the fuel.
U.S. Pat. No. 4,848,283, which issued to Garms et al on Jul. 18, 1989, discloses a marine engine with combination fuel return, crankcase pressure, and cooled fuel line conduit. The marine propulsion system includes a two cycle water cooled crankcase compression internal combustion engine including a vapor separator, a remote fuel tank, and a fuel pump in the tank for delivering fuel to the engine in response to the crankcase pulse pressure. A combination conduit between the fuel tank and the engine includes a first passage communicating crankcase pulse pressure from the engine to the fuel pump in the tank, a second passage supplying fuel from the pump in the tank to the engine, a third passage returning fuel vapor from the vapor separator at the engine back to the tank, a fourth passage supplying cooling water from the engine towards the tank, and a fifth passage returning water from the fourth passage back to the engine.
U.S. Pat. No. 4,865,004, which issued to Widmer et al on Sep. 12, 1989, describes a marine propulsion system with a fuel line cooler. The cooler is provided for a marine propulsion system having a water cooled internal combustion engine in a heat retentive compartment. The fuel line cooler has an inlet in communication with the source of cooling water for the engine, and has an outlet for discharging water. The fuel line cooler is cooled by sea water during running of the engine. Upon turn-off of the engine, the cooled water in the fuel line cooler is in heat transfer relation with the fuel and prevents vaporization and/or spewing of the fuel.
U.S. Pat. No. 4,875,439, which issued to Widmer et al on Oct. 24, 1989, discloses a marine propulsion system with a fuel line cooler that is generally similar to the system disclosed in U.S. Pat. No. 4,865,004 and described above.
U.S. Pat. No. 5,389,245, which issued to Jaeger et al on Feb. 14, 1995, discloses a vapor separating unit for a fuel system. The unit has particular application to a fuel system for marine engines. The vapor separating unit includes a closed tank having a fuel inlet through which fuel is fed to the tank by a diaphragm pump. The liquid fuel in the tank is controlled by a float-operated valve. An electric pump is located within the vapor separating tank and has an inlet disposed in the tank and an outlet connected to a fuel rail assembly of the engine. Excess fuel from the fuel rail assembly is conducted back into the upper end of the vapor end of the vapor separator tank. A vapor venting mechanism is incorporated in the tank to vent vapor from the tank.
U.S. Pat. No. 5,103,793, which issued to Riese et al on Apr. 14, 1992, describes a vapor separator for an internal combustion engine. The vapor separator assembly includes a bowl member and a cover member. The fuel pump is located in the internal cavity of the bowl member and has an inlet located in the lower portion of the bowl member cavity, for supplying fuel thereto. The fuel pump is secured in position within the bowl member by engagement of the cover member with the fuel pump. The cover member includes a mounting portion for mounting a water separating filter element to the vapor separator assembly. The cover member includes structure for routing fuel from the discharge of the water separating filter element to the interior of the bowl member cavity. A compact arrangement is thus provided for the vapor separator, the fuel pump, and the water separating filter, eliminating a number of hose connections between such components as well as facilitating assembly.
U.S. Pat. No. 5,443,046, which issued to White on Aug. 22, 1995, describes an efficiently pumped fuel supply system. In a low pressure continuous flow fuel injection system for an internal combustion system, an electric fuel pump is energized with a variable duty cycle to vary the pump volume output of the pump according to engine fuel requirements. The duty cycle is varied to energize the pump to pump substantially only the amount of fuel required by the engine, such that at idle or low engine speed, the pump is energized a lower percentage of the time than at high engine speed. Fuel flow through the fuel injector is continuous, but energization of the pump is not, such as the pump is not pumping at full capacity when unneeded. An electric idle air control valve is also energized with a variable duty cycle to vary the amount of bypass idle air supplied to the intake manifold.
U.S. Pat. No. 5,400,750, which issued to Jaeger et al on Mar. 28, 1995, describes a manifold and plenum construction for an electric fuel injected engine. The manifold includes a plurality of parallel runners, with each runner having a lower end communicating through a port in the cylinder head with a cylinder of the engine, and an open upper end. A fuel injector is mounted in each runner for injecting fuel into the runner. A plenum is mounted on the manifold and includes an upper wall and a lower wall which is spaced from the upper wall to define an air chamber. The upper ends of the runners communicate with the chamber, so that air is drawn from the chamber through the runners to the cylinders. A flange is spaced from the upper end of each runner, and the lower wall of the plenum is supported on the flanges so that the upper end of each runner projects into the plenum chamber. Hollow posts extend between the upper and lower walls of the plenum and bolts extend through the hollow posts and are threaded into the flanges on the runners in order to connect the plenum to the manifold.
U.S. Pat. No. 5,408,971, which issued to Jaeger et al on Apr. 25, 1995, discloses a fuel rail construction for an electronic fuel injected engine. The assembly includes an elongated rail having a longitudinal inlet passage and a longitudinal outlet passage. The upstream end of the inlet passage is connected to a fuel supply line while the downstream end of the inlet passage is connected through a pressure regulator to the upstream end of the outlet passage. A return fuel line is connected to the downstream end of the outlet passage. A plurality of injector bores communicate with the inlet passage and extend to the exterior of the rail and each injector bore receives one end of a fuel injector, while the opposite end of each injector is sealed within a bore in a runner of an intake manifold. The injectors are mounted in a manner to provide limited tilt to facilitate assembly with the bores in the fuel rail of the manifold reservoir.
All of the U.S. Patents described above are hereby expressly incorporated by reference in this description.
U.S. patent application Ser. No. 08/866,962, which was filed on Jun. 2, 1997, by White et al and assigned to the assignee of the present application discloses a fuel supply system for an internal combustion system. The fuel supply system is intended for use with a marine propulsion system having an electronically controlled fuel injection system. It eliminates the need for a vapor separator. The system pumps an excessive amount of fuel through a plumbed fuel supply loop and cools recirculated fuel to cool all of the components of the plumbed fuel supply loop, i.e. a continuous duty, constant displacement fuel pump; a pressure regulator; and a water separating fuel filter. Recirculated fuel flows from the pressure regulator to the water separating fuel filter as does make-up fuel from a fuel tank. The fuel stream from the water separating fuel filter flows to the low-pressure side of the fuel pump, which pumps the fuel through the plumbed fuel supply loop. A fuel injection portion of the fuel flows to the engine for combustion, while the remaining portion of the fuel is recirculated. The recirculated portion of the fuel is cooled, preferably using a water-cooled heat exchanger. The cooled, recirculated fuel passes through the pressure regulator and repeats its recirculation to the water separating fuel filter.
The fuel supply system described immediately above represents a significant improvement in performance over prior systems. However, it would be additionally beneficial if an improved version of the fuel supply system could be provided which reduces the volume of fuel stored within the fuel supply system when the engine is shut off, provides improved thermal characteristics to cool the liquid fuel and other components of the fuel system, and requires less volumetric space and a lower number of components than existing fuel systems.